The ghost penalty can also be applied to stabilize time-dependent problems, for which generally the mass form needs to be stabilized as well. In that case the scaling is chosen in such a way that the stabilization terms scale with the mesh parameter in the same way as the mass matrix; see (REF ). Similar to Schwarz preconditioning and aggregation, the ghost penalty can also be applied to provide inf-sup stable discretization of mixed formulations such as that of the Stokes problem; see, e.g., [1]}, [2]}, [3]}, [4]}.
Furthermore, the ghost penalty can also be applied to stabilize discretizations of codimensional manifolds,
such as partial differential equations posed on non-planar surfaces discretized with three-dimensional meshes; see, e.g., [5]}, [6]}, [7]}, [8]}.
